Kite

Due to security/privacy concerns, JSON REST API (WP API) only allows post meta data (custom field value) for authenticated users. 
This plugin is an easy way to make post meta available when unauthenticated.
After activate the plugin, go to WP API Customizer option page. 
Click the plus icon to add rows. 
Set JSON attributes and custom field names in your posts that you want to use when unauthenticated. 
The JSON REST API will provide the data as “post_meta” like the following:
<pre><code>"post_meta":{"your_attribute_a":"Custom Field A value","your_attribute_b":"Custom Field B value"}
</code></pre>

WP API Customizer

Make post meta data (custom field values) available for JSON REST API (WP API) when unauthenticated.

This plugin offers a simple interface to edit or delete any Custom Field names/keys you may have created in the post/page editor.
Deleting a Custom Field also deletes the associated content, so use with caution!
This is not meant to be a powerful plugin in the vein of <a href="http://www.advancedcustomfields.com/" rel="nofollow ugc">Advanced Custom Fields</a>.
Only users with role Editor and above have access to this plugin.

Edit Custom Fields

A simple interface to edit or delete Custom Fields.

WP API Customizer vs Edit Custom Fields